you can download host file without editing it and placed host file in etc folder from here .(strongly recommended for windows vista,7&8 user because he will not able to edit host file but he can replace the host file downloaded from here)

STEP 5 =>

now open idm again it will ask you to fill name e-mail address,serial key then fill that and click on ok

note: after clicking on ok if it will ask you that your host file is changed or damaged click on continue to repair or cancel then click on cancel instede of clicking on continue

by clicking on continue it will not converted into full version

Now check IDM, it should be converted to full version.

Note: In Windows 7 sometimes it denied access to write anything on hosts file, so first you must be logged in as Administrator and then change the file permissions of hosts file.